The chemical modification of surfaces to achieve desired chemical and/or physical characteristics has been previously described. U.S. Pat. Nos. 4,722,906; 4,973,493; 4,979,959; and 5,002,582 (the disclosures of each of which are incorporated herein by reference), for example, relate to surface modification by the use of latent reactive groups to achieve covalent coupling of reagents such as biomolecules and synthetic polymers to various substrates. The preferred latent reactive group is typically described as a photochemically reactive functional group (i.e., photoreactive group). When exposed to an appropriate energy source, a photoreactive group undergoes a transformation from an inactive state (i.e., ground state) to a reactive intermediate capable of forming covalent bonds with appropriate materials.
Such latent reactive groups can be used to first derivatize a desired compound (e.g., thermochemically), followed by the photochemical attachment of the derivatized compound to a surface. Such a sequential approach is suitable in many situations, but can lack such attributes as speed, versatility, and ease of use, particularly when used with target molecules that are inherently difficult to first derivatize.
Latent reactive groups can also be used to prepare photoactivatable heterobifunctional molecules as linking agents, e.g., having a photoreactive group at one end with a thermochemical attachment group at the other. (See, e.g., the above captioned '582 patent, and Reiner et al.)
Such linking agents can be used for either attaching nonreactive compounds to a surface or for priming a relatively inert surface in order to render it reactive upon exposure to suitable actinic radiation.
U.S. Pat. No. 5,414,075, commonly owned by the assignee of the present application, describes the use of linking agents to prime a surface to provide the surface with photoactivatable groups. This patent describes a restrained, multifunctional reagent useful for priming a support surface, or for simultaneous application with a target molecule to a support.
Reagents such as those described above, including those described in the '075 patent, are generally hydrophobic. As a result, they are of relatively low solubility in aqueous systems, thereby often limiting their usefulness to hydrophobic applications. In turn, linking agents of the prior art are rarely, if ever, coated in compositions that employ water as a primary (e.g., greater than about 50% by vol.) solvent.
On a separate subject, the preparation and use of a class of cationic polyelectrolytes is described, for instance, in "Polyamines and Polyquaternary Ammonium Salts", pp. 761-763, in Concise Encyclopedia of Polymer Science and Engineering, Kroschwitz, ed., John Wiley and Sons, 1990, the disclosure of which is incorporated herein by reference. Such polyamines and "polyquats" are described as being useful by virtue of their cationicity in applications involving interactions with anionically charged colloidal particles in aqueous media in nature. They are employed, for instance, in the flocculation of particulate matter from turbid natural waters, as pigment retention aids in the manufacture of paper, and as filtration aids, emulsion breakers, and so on.
Applicants are unaware of the existence of a nonpolymeric photoactivatable linking agent having both improved aqueous solubility and the ability to cross-link or bind otherwise nonreactive molecules to a surface.